As is well known to those of skill in the art, integrated circuits, i.e., electronic components, were fabricated in an array on a wafer. The wafer was then cut, sometimes called diced, to singulate the integrated circuits from one another.
Generally, the width of the scribe lines, which delineated the integrated circuits, was sufficient to accommodate the width of the saw cut plus tolerance in the positioning of the saw blade. Stated another way, the width of the scribe lines was sufficiently large such that the saw cut made by the saw blade was always within a scribe line.
When singulating the wafer from the front-side surface of the wafer, the saw blade was directly aligned with the scribe lines, which were visible to the operator and alignment system. Since the scribe lines were used directly to align the saw blade, the saw blade was aligned to the scribe lines to within tight tolerance. Accordingly, the scribe lines were relatively narrow and, more particularly, were only slightly wider than the saw blade. To illustrate, the width of the scribe lines was within the range of 0.002 inches (0.051 mm) to 0.008 inches (0.203 mm).
In certain instances, it was important to protect the front-side surface of the wafer during sawing, e.g., from shards and particulates generated during sawing. To protect the front-side surface, the wafer was sawed from the back-side surface of the wafer.
More particularly, to protect the front-side surface of the wafer, the front-side surface was attached to a tape. The tape supported the wafer during sawing.
The saw blade was aligned with the scribe lines on the front-side surface of the wafer using a two-step process. First, the tape was aligned with the scribe lines. The front-side surface of the wafer was attached to the tape. The tape had area greater than the area of the front-side surface such that the tape had an exposed region, which extended beyond the wafer.
The tape had alignment marks in the exposed region of the tape. As an example, see alignment holes 30a and 30b of Roberts, Jr. et al., U.S. Pat. No. 5,362,681, which is herein incorporated by reference in its entirety. In the above manner, the scribe lines were aligned with the alignment marks of the tape.
Second, the saw blade was aligned with the alignment marks of the tape. The wafer was then sawed with the saw blade from the back-side surface of the wafer. However, since the saw blade was aligned indirectly to the scribe lines using the alignment marks of the tape, a large tolerance was associated with the alignment of the saw blade to the scribe lines.
To accommodate this large tolerance, each of the scribe lines had a relatively large width. More particularly, the width of the scribe lines of the wafer designed to be cut from the back-side surface was significantly larger than the width of the scribe lines of the wafer designed to be cut from the front-side surface. To illustrate, the width of the scribe lines of the wafer designed to be cut from the back-side surface was approximately 0.012 inches (0.305 mm) or more.
Disadvantageously, forming the scribe lines with a relatively large width resulted in less integrated circuits for any given size wafer, i.e., there was a loss of yield of the integrated circuits from the wafer designed to be cut from the back-side surface. As a result, the cost of each of the integrated circuit was increased. However, it is desirable to minimize the cost of each integrated circuit.